Fix Concat for larger inputs and add an additional test

The old calculation of actual_idx was not correct because it didn't
consider the total number of executions on the x axis.

wonnx/templates/matrix/concat.wgsl

@@ -17,9 +17,9 @@ fn main(@builtin(global_invocation_id) global_id: vec3<u32>, @builtin(num_workgr
 	let gidx = global_id.x;
         let gidy = global_id.y;
 
-        let nx = num_workgroups.x;
+        let x_executions = num_workgroups.x * 16u;
 
-        let actual_idx = gidx + gidy * nx;
+        let actual_idx = gidx + gidy * x_executions;
 
 	{% for input in i_lens %}
 		{% if loop.first %}

wonnx/tests/concat.rs

@@ -35,6 +35,39 @@ fn test_concat() {
     common::assert_eq_vector((&result["Z"]).try_into().unwrap(), &expected_result);
 }
 
+#[test]
+fn test_concat_long() {
+    let n: usize = 100000;
+
+    let xdata: Vec<f32> = (0..n).map(|x| x as f32).collect();
+    let mut ydata: Vec<f32> = (n..2 * n).map(|x| x as f32).collect();
+    let input_dims = vec![n as i64];
+    let output_dims = vec![(n * 2) as i64];
+
+    let input_data = HashMap::from([
+        ("X".into(), xdata.as_slice().into()),
+        ("Y".into(), ydata.as_slice().into()),
+    ]);
+
+    let model = model(graph(
+        vec![tensor("X", &input_dims), tensor("Y", &input_dims)],
+        vec![tensor("Z", &output_dims)],
+        vec![],
+        vec![],
+        vec![node(vec!["X", "Y"], vec!["Z"], "a", "Concat", vec![])],
+    ));
+
+    let session =
+        pollster::block_on(wonnx::Session::from_model(model)).expect("Session did not create");
+
+    let result = pollster::block_on(session.run(&input_data)).unwrap();
+
+    let mut expected_result = xdata.clone();
+    expected_result.append(&mut ydata);
+
+    common::assert_eq_vector((&result["Z"]).try_into().unwrap(), &expected_result);
+}
+
 #[test]
 fn test_concat4() {
     let n: usize = 13;